Had to put that one back on the redo list as was a victim of my lousy weather the past 16 months. Haven't researched it as yet. I'll never get 10 hours on it even if the weather cooperates which it shows no indication of doing.

It is yellow for similar reasons to the Antares Nebula. Star type, dust particle size and light angle all contribute. The Antares Nebula (its main components) is the most obvious example of a yellow reflection nebula, but vdB 136 (here presented in glorious form by Mark), vdb 135, vdb 151, and the Toby Jug Nebula are other examples.

It's illuminating star, HD 196819, is listed as K2.5IIb (bright giant luminosity class) so a yellow orange star. We get so used to reflection nebula around blue stars it is easy forget they can be other colors. Of course other factors play in this, is this forward or backward scattering, what's the size distribution of the particles etc.?